Refactoring mojo tests.

-Replaced the way the MavenProject injected to a non-deprecated way (to get rid of the warning during the build).
-Updated mavenInvokerPluginVersion and extracted it as a pom-property.
-Extracted some RAT mojo integration test methods into a separate RatTestHelpers in order to find integration tests more easily after RAT-168 and the NPE when trying to forge 0.11.



git-svn-id: https://svn.apache.org/repos/asf/creadur/rat/trunk@1617370 13f79535-47bb-0310-9956-ffa450edef68
LHF: organized imports after refactoring.



git-svn-id: https://svn.apache.org/repos/asf/creadur/rat/trunk@1617371 13f79535-47bb-0310-9956-ffa450edef68